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In an earlier paper (59th AES-Convention Hamburg 1978) a procedure has been given for optimum transmission of speech and music into noisy environments, based on the characteristics of speech and music and on the characteristics of human hearing. The procedure involves processing of the speech and music signal by subjecting this signal to emphasis and compression, in order to match it to the environmental noise, thus enabling the transmission of the essential information of the speech and music through the noise to the listener, using a minimum of power and imposing a minimum of additional load on the hearing of the persons involved. For varying environmental noise the processing should vary in connection with the noise, thus maintaining matching of the transmission to the noise conditions, the latter being continuously sensed to obtain the control signal for noise controlled processing. This paper surveys the methods for noise controlled processing and for sensing the environmental noise. It introduces a new method for matching the processing to the noise conditions, complying with the requirements for optimum transmission (minimum power, minium load to hearing), and a new method for sensing the environmental noise during transmission of speech and music into that environment. These methods enable the transmission, maintaining the character of -Optimum Transmission,- to be matched to a wide range of environmental noise, either by manual operation or by automatic nosie controlled operation. Moreover, these functions could be embodied in a simple device, which could be inserted in most public address sound systems, thus allotting to these sound systems the important facility of optimum transmission in environmental noise without requiring any other extension than this device.